C# 14

It is especially relevant when adopting .NET 10 and modern APIs that rely on spans or expressive extension patterns.

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Extension members expand the extension model beyond classic extension methods.

public static class StringExtensions
{
    extension(string text)
    {
        public bool IsBlank => string.IsNullOrWhiteSpace(text);
    }
}

This makes extension-based APIs more expressive by supporting additional member shapes such as properties.

The field keyword makes it possible to add logic to an auto-property without declaring a separate backing field.

public string Name
{
    get;
    set => field = value ?? throw new ArgumentNullException(nameof(value));
}

Legacy style:

private string _name = "";

public string Name
{
    get => _name;
    set => _name = value ?? throw new ArgumentNullException(nameof(value));
}

Null-conditional assignment allows conditional assignment through a null-conditional receiver.

person?.Manager = newManager;
orders?[index] = replacement;

This removes some of the small guard if statements that used to be required.

C# 14 improves built-in support for Span<T> and ReadOnlySpan<T> so these APIs can feel more natural in everyday code.

ReadOnlySpan<char> text = "hello";
ReadOnlySpan<int> values = [1, 2, 3];

This is especially relevant in performance-oriented code, but it can also make span-based APIs easier to adopt more broadly.